(RNS) A Roman Catholic archbishop in Minnesota who had been one of the hierarchy’s most vocal opponents of gay rights is the target of an investigation into allegations that he had a series of sexual relationships with priests, seminarians, and other men.

The investigation of Twin Cities Archbishop John Nienstedt is being conducted by a prominent Minneapolis law firm hired by the archdiocese after church officials received an allegation against Nienstedt.

David Gibson

The archdiocese confirmed the investigation, which was first reported by Commonweal, a Catholic magazine based in New York.

Nienstedt, 67, said in a separate statement that the allegations “are absolutely and entirely false” and he said he himself authorized the internal investigation, which he called “independent, thorough.”

“The allegations do not involve minors or lay members of the faithful, and they do not implicate any kind of illegal or criminal behavior,” Nienstedt said. “The allegations involve events alleged to have occurred at least a decade ago, before I began serving in the Archdiocese of St. Paul and Minneapolis.”

Commonweal’s story cites Jennifer Haselberger, former top canon lawyer for Nienstedt, as saying she learned of the investigation when she was questioned by attorneys from the firm that the archdiocese hired, Greene Espel.

Nienstedt came under fire in September for allegedly failing to report or discipline clergy suspected of molesting children. Those allegations sparked ongoing criminal investigations. The allegations surfaced after Haselberger, who had resigned her post in frustration in April 2013, began leaking internal church documents that appeared to detail efforts to shield abusers.

One of Nienstedt’s top aides, the Rev. Peter Laird, quit. It later emerged that Laird did so after Nienstedt rebuffed his suggestion that the archbishop should resign.

But late last year, the archdiocese received an unrelated allegation that Haselberger said turned up other accusations against Nienstedt, who was ordained a priest in Detroit before becoming a bishop in Minnesota.

“Based on my interview with Greene Espel—as well as conversations with other interviewees—I believe the investigators have received about ten sworn statements alleging sexual impropriety on the part of the archbishop dating from his time as a priest in the Archdiocese of Detroit, as Bishop of New Ulm, and while coadjutor/archbishop of St. Paul and Minneapolis,” Haselberger told Commonweal.

She added that “he also stands accused of retaliating against those who refused his advances or otherwise questioned his conduct.”

Contacted by e-mail, Haselberger confirmed the magazine’s account.

In a written response to Commonweal, Nienstedt dismissed the charges as a “personal attack against me due to my unwavering stance on issues consistent with church teaching, such as opposition to so-called same-sex marriage.”

He said he also suspects that accusers are making claims because of “difficult decisions” he has made. He told the magazine he could not elaborate because of privacy laws.

In December last year Nienstedt was accused of touching a boy’s buttocks while posing for a confirmation photo. He denied the allegation and took a leave while the county prosecutor investigated. The authorities did not bring charges and Nienstedt returned to his post in March.

Nienstedt has earned a reputation as a leading culture warrior in the U.S. Conference of Catholic Bishops and his signature issue is homosexuality.

He frequently discusses the topic, often using controversial language or espousing unorthodox theories. He has said, for example, that homosexuality is not genetic but is a “result of psychological trauma” when a child is between the ages of 18 months and 3 years old.

Homosexuality, he has written, “must be understood in the context of other human disorders: envy, malice, greed, etc.”

In 2006, while bishop of the New Ulm diocese, he wrote a column warning the faithful against watching Brokeback Mountain, the story of two gay cowboys struggling with their relationship in the conservative culture of the Mountain West.

He decried the depiction of how “one man makes a pass at the other and within seconds the latter mounts the former in an act of wanton anal sex,” and he said Hollywood’s trendmakers “have turned their backs on God and the standards of God in their quest to make evil look so attractive.”

Then in 2010, Nienstedt launched a major campaign ahead of the midterm elections that focused on opposing gay rights, and he told a mother who wrote to him asking for tolerance for her gay son that she should instead read the Catechism of the Catholic Church and consider her “eternal salvation.”

In 2012, Nienstedt led religious leaders in pushing for an amendment to the state constitution that would have effectively banned gay marriage. He committed $650,000 in church funds to the effort but it divided his own flock and the backlash is believed to have contributed to the amendment’s defeat.

A year later, Haselberger began publishing her memos and Nienstedt has been embroiled ever since in questions about his handling of sex abuse cases.

There is one link between the investigations: the lawyers are looking at whether Nienstedt had a relationship with the Rev. Curtis Wehmeyer, a priest with a history of inappropriate sexual behavior who Nienstedt named to head two different parishes. Wehmeyer molested children at one of the parishes.

Nienstedt told Commonweal that his relationship with Wehmeyer was “professional” and “pastoral” and preceded the reports of Wehmeyer’s abuse.

In his statement Tuesday (July 1), Nienstedt said that he had informed Pope Francis’ representative to the U.S. of the charges and the investigation, and said the final report would be given to the Vatican ambassador to pass along to Rome.

He did not say whether he would make the report public, adding only: “Let us pray that the truth will come out as a result of the investigation.”